Recent debates regarding the potential dangers of generation, propagation and consumption of genetically-modified organisms (GMOs) have led to a perception among some consumers that GMOs, and the food products derived from them, are in some way dangerous or unhealthy. For example, recent restrictions on the import of GM foods into Europe have withdrawn an important market from farmers raising genetically modified food crops and animals. Thus, in spite of the agronomically superior traits of some GMOs, farmers may choose to raise non-transgenic plants and animals rather than risk a drop in demand for genetically-modified (GM) foods.
Transformation of organisms typically involves the introduction of a gene of interest (i.e. a “payload” gene) and a selectable marker into the organism. The selectable marker gene is useful in the transformation process to select for, and identify, transformant organisms, but typically provides no useful function once the transformed organism has been identified. In contrast, the goal of transformation technology is to introduce and maintain the payload gene into an organism. PCT Application No. WO 97/37012 describes a system for removing selectable marker genes in transgenic plants by flanking the selectable marker gene with recombination sequences. Following expression of a recombinase, the selectable marker gene is excised, thereby providing a transgenic plant with the associated gene of interest but lacking the selectable marker.
In light of the issues raised by GMOs, there is a need for methods of producing organisms with the advantages of genetic engineering that produce non-transgenic products. The invention presented herein addresses this and other problems.